Two-Dimensional FDTD Inverse-Scattering Scheme for Determination of Near-Surface Material Properties at Microwave Frequencies

This paper reports a two-dimensional time-domain inverse-scattering algorithm based upon the finite-difference time-domain method for determining near-surface material properties at microwave frequencies. The time-domain nature of this technique allows for limiting the region of inversion using causality. The algorithm traces a search trajectory in the (/spl epsiv//sub r/, /spl sigma/) parameter space. The minimal parameter estimation error along this trajectory yields a set of approximate parameter values. It is shown that the algorithm's convergence and robustness with respect to broadband Gaussian noise depends on the shape and the duration of the illuminating electromagnetic wave pulse chosen for the electrical parameter reconstruction. It is possible to achieve an unambiguous indication of algorithm convergence despite the noisy background.